In ancient Rome, tyrannical Emperor Caligula is assassinated through the machinations of Messalina. She then makes a conquest of Marcus, who forces the Senate to name her husband, Claudius, as emperor. Messalina's wicked ways continue when she falls in love with Ennio, a slave. Ennio is also loved by Egyptian princess Mirit, but he loves neither of them, preferring the company of Ela, a Greek slave.